Study On 3D Direct Writing And Properties Of Emulsion Energetic Binder System/CL-20 Based Explosive Ink

Micro Electro-Mechanical Systems(Micro Electro-Mechanical Systems)pyrotechnics with both miniaturization and intelligence are highly compatible with the needs of future weapons and equipment to be lightweight,intelligent,and high damage.It has broad application prospects in the miniature detonation system of future weapons and equipment.Direct writing technology has the characteristics of simple process,safety,flexible manufacturing,and has become the main charging method for MEMS explosives.In this paper,micro-detonation explosive as the research object,we designed and prepared a Polyvinyl alcohol(PVA)aqueous solution/Glycidyl azide polymer(GAP)ester solution“oil-in-water”emulsion type energetic binder system by emulsification technology.The high-efficiency compounding of nano-CL-20particles and binder system was realized by planetary gravity mixing technology.The direct-writing molding process and the curing mechanism of the energetic compound were studied.The molding effect,safety performance,mechanical properties and detonation performance of the micro-size charge were tested and analyzed.The details content are as follows:(1)The aqueous solution of PVA as water phase,the ethyl acetate solution of GAP as oil phase,the combination of Tween-80 and sodium dodecyl sulfate(SDS)as emulsifier,bis-propargyl-succinate(BPS)as a curing agent of GAP,a PVA/GAP oil-in-water(O/W)emulsion-type binder system was designed and prepared.The L₉(3~4)orthogonal experiment was designed by SPSS software to optimize the emulsification process and component ratio,and the optimized emulsion preparation process was obtained as follows:The mass ratio of Tween-80/SDS is about 1/3,the content of emulsifier is 1.5%,the concentration ratio of water phase and oil phase is 8/4,and the emulsification temperature is 25°C.Under the optimized process conditions,the stationary stability time of emulsion is about 144h,the dispersed phase droplets are uniformly dispersed,and the particle size distribution is between 20?80?m.(2)The CL-20 explosive was refined by the mechanical ball milling method,and the submicron CL-20 explosive particles with particle size between 200?400 nm were obtained.Planetary gravity mixing technology was used to mix submicron CL-20 explosive and the emulsion binder system and prepared CL-20 based explosive inks with different solid contents,their rheological properties were tested and analyzed.The theoretical detonation velocities of the molded samples with different explosive content were calculated.The results show that the theoretical detonation velocity and rheological properties are excellent when the content of CL-20 is 90 wt.%.Planetary gravity mixing technology is an efficient method to achieve minute quantity mixture of nano-particle explosive ink.Compared with traditional paddle mixing process,this technology has the advantages of good mixing and dispersing effect and high efficiency.(3)The single-factor experiment method was used to study the influence of 3D direct-writing molding process on the direct-writing molding effect.On this basis,the optimal process conditions were determined as follows:18 G tapered needle(inner diameter around 0.8 mm),drive air pressure is 0.4 MPa,direct writing speed is 8 mm/s,needle height is 0.4 cm from the substrate,and substrate temperature is 50°C.With the best direct writing process,the line,plane pattern and three-dimensional structure were direct writing and formed.The results show that CL-20 based explosive ink has a favorable direct writing effect,can realize the forming of three-dimensional grid structure with a certain self-supporting capability.The direct writing line width is about 700?m,and the relative deviation is 2.15%.(4)The microstructure,crystal form,mechanical strength,thermal decomposition performance,and safety performance of CL-20-based explosive ink molded samples were characterized and tested.The detonation transfer ability of the molded samples under the microscale was systematically studied.The results show that the surface of direct writing samples is smooth and the interior is uniform and dense,the crystal form of CL-20 is?-type.Its elastic modulus and hardness are 6.776 GPa and 0.143 GPa,respectively.The apparent activation energy is increased by about 7.2 k J·mol^-1 compared with the refined CL-20,and the thermal stability is improved.The impact sensitivity,friction sensitivity and electrostatic sensitivity of the molded samples are all lower than those of raw material CL-20 and refined CL-20,its safety performance is favorable.When the charge width is 1 mm and the charge density is 1.627 g·cm^-3,the critical detonation thickness of the molded sample is 0.045 mm,the detonation velocity can reach 7129 m·s^-1,the critical detonation angle is 150°.It can be transmitted through continuous 90°corners and realized reliable detonation,shows excellent micro-scale detonation capability.